This Hypoxia-Hypercapnia Core will serve the 4 Projects in the Program in various ways. Core C will provide mice (or rats) that have been exposed to hypoxia or hypercapnia (or both) in a standardized and consistent way. Moreover, the Core will promote interactions among the investigators and help generate new avenues of collaborative investigation because of the use of identical models to study mechanisms for response and adaptation to long-term and graded stress. The aims of this Core Facility are as follows: 1. To ensure a consistent experimental model of chronic hypoxia or hypercapnia or both for use in all four projects; 2. To train technicians and postdoctoral and help in tissue dissection and collection for all investigators whether brain, heart or kidney; 3. To continue to characterize the chronic hypoxia-hypercapnia model in order to better understand the implications of novel findings that arise during the course of this program; 4. To develop comparable models of chronic hypoxia or hypercapnia in mice with genetic alterations (e.g. Knock-out such as NHE-/-) to propose specific mechanisms for adaptation or injury; 5. To help investigators in the design of experiments requiring chronic exposure of cells in culture for an extended period of time in hypoxia, hypercapnia or both.